4. Click on the +1 button and wait for a small popup to appear that says "You publicly +1'ed this as [your name]. Share what's new".

5. Click on it and type an optional comment.

6. In the field where it shows + Add more people, make sure you have selected "Public"

7. Click "Share".

How to share a page that does not have a +1 sharing button?

If you like to share any page that does not have a +1 sharing button, you can go directly to your Google+ profile and type the URL that you want to share in the field that says "Share what's new". This field is located under the heading "Stream" in your Google+ Profile.]

Important: Verify your Google+ Profile

In order to verify you are the owner of the Google+ Profile you specified in your Social Settings page, you should publicly share your profile page from this site to your Google+ profile and should not delete the sharing.